So-called round link chains are composed of concatenated individual round links. Respective adjacent chain links are rotated by 90° with respect to one another relative to the longitudinal axis of the chain. Each chain link of a round link chain consists of a bent wire section, the free ends of which are butt-welded to one another.
In a plan view onto the flat side, the chain link consists of two straight mutually parallel sections, both transitioning at each end into semicircular arcs. The radius of the two semicircular arcs corresponds to the center separation of the straight sections. The projection of such a flat-lying chain link onto a plane parallel to the flat side of the chain link is bounded by two lines, one of which is an outer line and the other of which is an inner line. The outer line is consequently composed of two straight sections that are mutually parallel and two semicircular arcs, the diameter of which corresponds to the distance between the straight sections. The inner line runs the same distance away from the outer line at every point, corresponding to the wire diameter.
Such round link chains can be used for moving workpieces or as carriers. The carriers can be, for instance, pallets that are transported along a conveyance path. The chains also can be used as a load-carrying mechanism of a so-called chain hoist.
Round link chains are driven via chain sprockets, which cooperate in a positively engaged manner with the chain links. A distinction is made in this regard between vertical chain links and horizontal chain links. This distinction is made from the perspective of the chain sprocket. A horizontal chain link is understood to mean a chain link of which the flat side is turned towards the axis of rotation of the chain sprocket. A vertical chain link is a chain link for which the flat sides are perpendicular to the axis of rotation of the chain sprocket.
In previously common chain sprockets, only the horizontal chain links have been used to transmit the force from the chain sprocket to the chain. The vertical chain links have so far not been used for force transmission for chain sprockets and round link chains.
A chain sprocket is known from EP 0 269 557 A1 that is adapted to the change of chain pitch resulting from wear on the chain. When the chain under load passes over the chain sprocket, a movement occurs between adjacent chain links. The movement arises because the chain that is stretched under a load is forced by the chain sprocket into a circular path. The relative motion between the chain links causes frictional wear, with the result that the thickness of the chain link is reduced in the areas experiencing the friction. The thickness of the chain link is understood in the art to mean the diameter that the wire has at the point in question. The chain becomes longer due to the change of the chain link thickness, i.e., its periodicity no longer matches the pitch of the chain sprocket. To take this into account the chain pockets for the vertical chain links are specially formed in the known chain sprocket.
The chain pockets for the vertical chain links form a channel running in the circumferential direction of the chain sprocket that passes through the chain pockets for the horizontal chain links. The bottom of this groove describes an n-gon in the broadest sense, n being equal to the number of chain pockets for the horizontal chain links. Each of the sides of this regular n-gon is a circular arc segment with a constant radius of curvature that is very large with respect to the radius of curvature of the outer line of the individual chain link. The bottom of the pocket has no radius of curvature along its extent. It merely transitions at one end into a rounded corner of the n-gon, at which the next pocket bottom for the adjacent chain pocket of a vertical chain link begins. This corner can also be understood as a tooth in the broadest sense. The tip of the tooth is situated centrally, i.e., centered in the pocket for the horizontal chain link. It ends clearly below a plane that is defined by the flat side of the chain link closest to the axis of rotation.
FIG. 2 of the aforementioned EP 0 269 557 A1 shows the relationships between the vertical chain link and the associated chain pocket when a previously unused round link chain is used. The adjacent horizontal chain links hold the vertical chain link a distance above the bottom of the chain pocket for the respective vertical chain link. Only if the chain lengthens due to wear does a slight tilting of the vertical chain link occur, with the consequence that the chain link contacts the bottom of the pocket with its nose pointing in the load direction. The tangent at the contact point between the pocket bottom and the outer line of the chain link runs at a very acute angle to the longitudinal axis of the vertical chain link, whereby almost no force introduction from the chain sprocket to the round link chain via the point-shaped contact location is possible. The known chain sprocket is thus not capable of utilizing the chain to a higher degree than that which corresponds to the standards according to the safety limit values. The standards assume that the highest stress on the chain occurs in the area of the chain sprocket.